The invention relates to a turbine having an impeller, wherein a pressure distributer is arranged on the rear side of the impeller. The turbine can be used for example within a waste-heat recovery system for utilizing the waste heat of an internal combustion engine.
Turbines having a housing and an impeller arranged in the housing are known from the prior art, for example from patent EP 1 281 836 B1. The known turbine has an inflow region and an outflow region and a working medium flows through said turbine during operation. The working medium flows into the inflow region, along a front side formed on the impeller and subsequently out of the outflow region, wherein there is a pressure drop on the front side between the inflow region and the outflow region. Furthermore, the known turbine has at least two control valves which are controlled by a controller and control the pressure onto a rear side of the impeller. Consequently, the resulting aerodynamic flow acting on the impeller can be controlled in such a way that the resulting axial force, also termed axial thrust, is minimized. Accordingly, an axial bearing of the shaft is less loaded or the axial bearing can be dimensioned to be smaller.
Furthermore, a turbine having a pressure distributer is known from patent application DE 10 2014 226 951. The pressure distributer is arranged on the rear side of the impeller. The pressure distributer comprises a sliding ring which interacts with the rear side and thus forms a vapor-lubricated throttle. A first flow path runs through the throttle, wherein the throttle divides the rear side hydraulically into a first region and a second region. The first region delimits the inflow region, and the second region delimits a pressure chamber. The two regions are configured in such a way, that is to say separated by the throttle, that different pressures can be applied to them. During operation of the turbine, the inflow region is loaded with a higher pressure than the pressure chamber. The sliding ring is mounted in an axially movable or floating manner. A sealing ring arranged in a groove interacts with the sliding ring. A second flow path from the inflow region to the pressure chamber runs between the groove and the sliding ring. The second flow path can be closed by the sealing ring.
By virtue of the pressure distributer, the axial force acting on the impeller can be kept virtually constant. However, the axial movement of the sliding ring means that the sealing ring of the known turbine during operation is very highly loaded and thereby exposed to an increased risk of wear. Furthermore, the sealing function is therefore not robust over all operating pressures.